Please check following items:
- Disconnect and reconnect the audio source. If you have a projector and are using the RF input, disconnect and reconnect the RF cable.
- Connect the audio source to a different speaker system, such as headphones or a different TV/ projector and verify if the audio source is the cause of the problem.
- Try using a different audio cable to verify that the current one you are using is not faulty.
- Connect a different audio source to the monitor/TV and verify if the problem persists.